class UserDAO:
'''
A DAO (Data Access Object), providing a Data Abstraction Layer
for the system's user entities. Implementation assumes a MongoDB
and thus implements the requires operations using Mongo-DB queries and
uses the MongoDAO as a helper class.
@see MongoDAO
'''
def __init__(self, db_connection):
self.db_connection = db_connection
def init(self):
''' Late-initialize; Must be called after the DB connection has been established. '''
self.mongo_dao = MongoDAO(UserEntity, self.db_connection.get_connection(), UserEntity._db, UserEntity._collection)
self.collection = self.mongo_dao.collection()
del self.db_connection
def create_user(self, user_name):
''' Create a new user. '''
entity = UserEntity()
entity.name = user_name
return self.mongo_dao.create_entity(entity)
def get_user(self, user_id):
user = self.mongo_dao.get_entity(user_id)
if not user:
raise NoSuchUser(user_id)
return user
def add_follow(self, user, follow_uid):
# Trouble with trying to implement this directly via the ORM - as follows:
# user.following.append(follow_uid)
# user.save()
# So a manual implementation is used instead.
query = {"_id":user._id}
update = {'$push':{"following":follow_uid}}
self.collection.update(query, update);
user = self.get_user(user._id)
def remove_follow(self, user, follow_uid):
# This could have easily been implemented directly via the ORM as follows:
# user.following.remove(follow_uid)
# user.save()
# BUT! the ORM appears to be buggy!!! So have have to do this manually
query = {"_id":user._id}
update = {'$pull':{"following":follow_uid}}
self.collection.update(query, update);
user = self.get_user(user._id)
def add_post(self, user, post):
''' Add a new post (post-type agnostic).'''
# The ORM fails a great deal in dealing with these complex queries, so
# we have to do this manually
query = {"_id":user._id}
update = { '$push':{ "posts":{'$each':[post.get_dict()], '$sort':{"created":-1}, '$slice':-100000}} }
self.collection.update(query, update);
user = self.get_user(user._id)
def get_followed_users(self, user):
'''
Retrieve the list of users (data and everything) followed by the given user.
Returns the users as a list of UserEntity objects.
'''
if not user.following or len(user.following)==0:
return []
# A 'get' of multiple keys: this is definitely too tricky for the ORM to handle,
# so we do both this and the 'translation' manually
# Build query string; final form of it should be like so:
# { $or : [ {_id:X}, {_id:Y}, {_id:Z} ] }
# Which would lookup users whose ID's are in this set: (X, Y, Z).
query = []
for f_user_id in user.following:
query.append({'_id':f_user_id})
query = {'$or': query}
docs_cursor = self.collection.find(query)
users = []
for doc in docs_cursor:
ent = UserEntity().set_from_dict(doc)
users.append(ent)
return users
def init(self):
''' Late-initialize; Must be called after the DB connection has been established. '''
self.mongo_dao = MongoDAO(UserEntity, self.db_connection.get_connection(), UserEntity._db, UserEntity._collection)
self.collection = self.mongo_dao.collection()
del self.db_connection
